In a 5-4 ruling on June 11, 2001, the US Supreme Court ruled that the use of thermal imaging (infrared)
scanners to look at homes for evidence of crimes is unconstitutional without a warrant. The majority
issued a broad decision, suggesting that other types of high-tech gear which reduce privacy
in the home are also disallowed without a warrant. This decision reverses a set of flip-flopped 9th
Circuit Appeals Court decisions where the 9th Circuit first found in favor of Kyllo and then, after a judge
resigned, it reheard the case and decided against Kyllo.

The decision was made by an unusual coalition of justices, with Scalia writing the majority opinion,
quoting from elements of the ACLU's amicus brief in favor of increased Constitutional rights and
Stevens, in dissent, arguing that the Right to Privacy does not protect against scanning devices.
Two of the most conservative justices, Scalia and Thomas joined with the
more liberal Ginsburg, Breyer, and Souter and the liberal Stevens and moderate Kennedy
joined with Rehnquist and O'Connor in dissent.

Scalia's broad opinion argues that technology has weakened the privacy of citizens and
"The question we confront today is what limits there are upon this power of technology to shrink
the realm of guaranteed privacy. To withdraw protection of this minimum expectation would be to
permit police technology to erode the privacy guaranteed by the Fourth Amendment." Justice Scalia and the majority opinion then proposes a standard for checking the constitutionality of search/detection equipment:

We think that obtaining by sense-enhancing technology any information regarding the interior of the home that could not otherwise have been obtained without physical "intrusion into a constitutionally protected area",(Silverman, 365 U.S., at 512), constitutes a search-at least where (as here) the technology in question is not in general public use.

This proposed rule mirrors that proposed by the ACLU's amicus (friend of the court) brief and,
if it becomes a nationwide standard, would offer a great deal of privacy protection to citizens
of the U.S.

The government prosecutors and the dissent argue that the use of thermal scanners does not require
a warrant because it only looks at things which are in 'public view'. They argue for a distinction
between "through-the-wall" and "off-the-wall": where 'through' constitutes a search where 'off' would
not. I was unable to decipher what these distinctions would actually mean and think that Stevens is
perhaps somewhat confused. The argument seem to be based on the faulty assumption that the technology for scanning
inside boxes, homes, or other private areas are somehow limited in type and scope by the antiquated concept of
"inside" and "outside": technologies available now are able to see through walls, record conversations inside
buildings, read computer monitors and keyboards from the signals they put off, etc. Which of these
are 'off-the-wall' and which 'through-the-wall' ? Is the argument of the dissent actually that anything
that is detectable without putting equipment 'inside' a space fair game?

What Stevens's argument seems to lead to is that we all would need to line our homes with layers of lead,
thermal insulation, and noise-deadening material in order to reasonably expect privacy from the
prying gaze of government agents with up to date technology.

Stevens offers the argument that thermal imaging is distinct from using listening devices because
the level of detail is so much different:

Surely, there is a significant difference between the general and well-settled expectation that strangers will not have
direct access to the contents of private communications, on the one hand, and the rather theoretical expectation that an occasional
homeowner would even care if anybody noticed the relative amounts of heat emanating from the walls of his house, on the other.

But Stevens appears to be ignoring the fact that many homeowners probably would, in fact, choose to
keep rogue government agents (without cause enough for a warrant from a judge) from scanning their homes
to determine what devices or activities ar used inside, even if the information is general and vague.
While there is certainly a difference between intercepting communications and general scanning,
the Orwellian overtones to the possibility that the government could use any technology it wanted to
spy on citizens is what this case seems all about.

The other primary government argument is that the technology used is too blunt to be able to detect
with specificity "private activities or things". A classic element of 4th Amendment law is the concept
of sexual or "intimate" things which are regarded as receiving the highest level of protection.
While its certainly true that the devices they were
using were quite crude compared to some of the listening and viewing technologies which are
just becoming available and will be in the future, I'm certain that Kyllo wanted to keep his cannabis
garden private and had it inside in order to make it so.

Scalia, however, argues that the distinction drawn by the Dissent can't be a workable standard because
there is no direct connection between the resolution and precision of the scanning and the intimacy or
privacy of the details exposed:

To begin with, there is no necessary connection
between the sophistication of the surveillance equipment and the "intimacy" of the details that it observes--which means that one
cannot say (and the police cannot be assured) that use of the relatively crude equipment at issue here will always be lawful. The
Agema Thermovision 210 might disclose, for example, at what hour each night the lady of the house takes her daily sauna and
bath-a detail that many would consider "intimate"; and a much more sophisticated system might detect nothing more intimate than
the fact that someone left a closet light on.

Stevens, in his dissent, suggests a different, looser standard:

I would not erect a
constitutional impediment to the use of sense-enhancing technology unless it provides its user with the functional equivalent of
actual presence in the area being searched.

Stevens ends his dissent with an agreement that the technology threatens privacy, but argues
that the protection of privacy should be left up to the legislature and not decided by the Court
in this way. It will be interesting to see whether the legislatures in the US choose to address
the problem of technology reducing privacy and how the courts use this ruling.